As radiation arrives from Japan, what level is safe?

SALT LAKE CITY — Although no definitive evidence exists that radiation from Japan has reached Utah, local officials believe it has arrived in extremely tiny amounts, barely detectable over natural background levels.

Local experts say they see no health threat from the radiation so far. But the radiation drifting to the U.S. from a troubled Japanese nuclear power plant has opened up an old scientific debate: Is any level of radiation, no matter how small, safe for humans?

There is a scientific consensus, of sorts, on that issue. But it's a very shaky one.

In Utah, the evidence of radiation from Japan is sketchy. Last weekend, real-time radiation detectors in Milford, Delta and St. George showed barely observable increases in Gamma radiation. The state is waiting for more definitive data to be analyzed from a Salt Lake City monitoring station. Filters from that monitor have been sent to an EPA lab in Alabama, along with a liter of rainwater from storms last weekend.

Radiation monitors frequently detect slight variations in the natural background level. The radiation sometimes jumps to as much as twice the normal rate, due to natural phenomena such as windstorms and solar activity. But state officials suspect the blip in the radiation level is from Japan this time, because other states have found clear evidence that it's arrived.

Rusty Lundberg, Utah’s director of radiation control said, "I think, given what others are seeing in the West … I think that we could say that, in all likelihood, it could be part of what we'd see here in Utah" from Japan.

No one doubts a much larger release of radiation in Japan could be deadly. Many studies clearly show that high levels of radiation cause cancer. But the risks of very low level radiation are much less understood.

“Most scientists in that field would accept the concept that there is not a safe level of exposure. Even though at low doses it's going to be small, that doesn't mean there's a safe level," said Dr. Brian Moench, president of Utah Physicians for a Healthy Environment.

"There is disagreement about that," said Peter Jenkins, a health physicist who chairs the Utah Radiation Control Board. "Less than about 100 times background (level) we consider that a low dose, and the cancer risk isn't considered significantly greater."

The National Academy of Sciences tried to answer the question definitively in a 2006 report. Analyzing all existing studies, the academy concluded, "The smallest dose has the potential to cause a small increase in risk to humans."

That principle underlies government regulation in the nuclear industry. Exposure limits are set based on a presumption that any level of exposure to radiation raises the risk of cancer, however slightly.

Jenkins says that's an appropriate basis for government safety policies. But from a scientific point of view, he believes the statistical basis for it is weak. He points out that nearly half of all humans get cancer anyway. A tiny increase in cancer might be statistically insignificant because slight variations in cancer rates happen, naturally, all the time.

"The uncertainty is so great that it allows for both statements to be made," Jenkins said, “safe or not safe.”

Moench argued that industry and government regulators have historically downplayed the risks and that unbiased scientists accept the theory that no level of radiation is truly safe. He also said low-level radiation has a cumulative impact on health. "The number of times you're exposed adds up,” Moench said, “and adds to your cancer risk."

He said the greatest risks are to fetuses and reproductive cells. Moench believes that declining fertility rates may be one consequence of low-level radiation increases in the last few decades.

Jenkins argued that such fears could drive people away from legitimate uses of radiation. When a doctor recommends X-rays or CT scans to a patient suffering symptoms of an ailment, Jenkins said, the benefit of using the diagnostic procedure clearly outweighs the risk of the radiation.